tillation should be such that about 2 grams of distillate collect per minute.
The weight of the distillate Up to 310° is determined.
If the mineral oil contains much water, it is convenient to dehydrate
it by means of calcium chloride and to decant it before distillation in order
to avoid bumping during the heating.
3. Flash Point.—The flash point of an oil is the temperature correspond-
ing with the initial evolution of vapour forming with air a mixture capable
of exploding in contact with a flame, or, more accurately, the temperature
at which such vapour can be detected under definite experimental con-
This determination is made with crude petroleum as with light oils (see
later). With crude petroleums poor in light oils, however, the high flash
point requires the use of the apparatus employed with lamp oil or heavy
oils (see the paragraphs concerned).
4. Temperature of Ignition.—This is the temperature at which the
mineral oil, coming into contact with a flame, ignites and continues to burn.
For its determination, see Light Mineral Oils.
5. Calorific Power.—As a rule this is determined only when the crude
petroleum is to be used as a fuel, as is the case with that from certain localities
(Texas, California) ; the Mahler bomb calorimeter is used (see Fuels). If
the petroleum is poor in light oils, 1-1-5 gram of it is weighed directly into
the capsule for holding the fuel, but if rich in volatile matter it is well to
weigh it in a small glass bulb with the ends drawn out, the igniting wire
being passed through the bulb ; the bulb is placed in the capsule and just
before the bomb is closed the two ends are broken in order to facilitate
access of the oxygen to the liquid.
2. Chemical Tests
1. Determination of the Water (Marcusson's method).1—100 c.c.
of the product are mixed with 50 c.c. of xylene and the mixture distilled,
in presence of a few scraps of pumice, best in an oil-bath until the water
passes over. The distillate is collected in a graduated cylinder and the
volume of the lower aqueous layer measured.
2. Determination of the Suspended Solid Matter.—The oil is
shaken with at least 20 times its volume of benzene (to dissolve any sus-
pended pitch and asphalt), filtered after standing for some hours, and
the residue on the filter washed with benzene, dried and weighed.
3. Determination of the Sulphur.—This may be carried out by
Eschka's method (see Fuel) or in the Mahler calorimetric bomb. With
Eschka's method, I gram of the mineral oil is mixed with sufficient of the
mixture of magnesia and sodium potassium carbonate to give a dry powder,
which is covered, in the crucible with a layer of the mixture.
In the bomb, the determination is made simultaneously with that of
the calorific power, the sulphur undergoing conversion to sulphuric acid.
When the combustion is complete, the gas formed is passed through about
25 c.c. of 8% potassium carbonate solution, the apparatus being then rinsed
1 J. Marcusson: Laboratoriumsbuch fur die Industrie der Oele und Fette (1911).
A.c, 22oduced into .the inner tube and allowed to cool slowly